The present invention relates to a synchronizing control system for a thrust reverser of an aircraft turbojet engine, more particularly, such a synchronizing control system mechanically interconnecting at least two thrust reverser doors.
Turbofan-type turbojet engines are well known in the art and typically comprise a fan at the front of the turbojet engine which directs a flow of bypass air through a duct bounded by the engine cowling on the inside and a fan cowling on the outside. The generally annular duct bounded by the engine cowling and the fan cowling may channel both the bypass flow and the primary exhaust gas flow at a downstream portion from the turbojet engine, or may channel only the bypass flow.
In aircraft on which the turbojet engine is mounted outside of the airframe structure, the fan cowling and the engine cowling are configured to form boundaries of the bypass flow duct and to provide aerodynamic outer surfaces to reduce drag.
FIGS. 1 and 2 illustrate a known pivoting door-type thrust reverser associated with the cowling of a turbofan-type turbojet engine. As illustrated in FIG. 1, the upstream portion of the cowling which defines the outer limits of the bypass flow duct and which is generally concentrically arranged about the turbojet engine (not shown) is designated as 1 and generally comprises an external cowling panel and an internal cowling panel interconnected by a frame 6. The outer surface of the external cowling panel has an aerodynamic surface over which the air external to the engine passes during aircraft flight. The inner surface of the inner cowling panel defines the outer boundary of the bypass flow duct 15 through which the bypass flow air passes in the direction of the arrow.
The cowling also comprises a thrust reverser, illustrated generally at 2, and a downstream cowling portion 3. The thrust reverser 2 comprises a door 7 pivotally attached to the cowling so as to pivot about transverse axis 17 such that it is movable between a closed, forward thrust position, illustrated in FIG. 1, and an open, reverse thrust position in which the forward end (towards the left as viewed in FIG. 1) of the thrust reverser door 7 is moved outwardly from the cowling, while a rear portion is moved inwardly into the bypass flow duct airstream so as to redirect at least a portion of the bypass flow through an opening in the cowling in a direction that has a reverse thrust component.
An actuator 8 for moving the door 7 between its forward thrust and reverse thrust positions may comprise a cylinder extending through and mounted to the frame 6, and having an extendable and retractable piston rod connected to the thrust reverser door 7.
The thrust reverser door 7 has an outer door panel 9 and an inner door panel 11 joined together by an internal structure. The forward end of the door 7 may have a deflector to maximize the efficiency of the thrust reverser when the door 7 is in the reverse thrust position. When the door is in the forward thrust position, as illustrated in FIG. 1, the outer door panel 9 is substantially flush with the external surfaces of the upstream panel and the downstream cowling portion 3. The inner face 11 tapers toward the outer surface 9 at the forward end of the door 7, forming a cavity when in the forward thrust position.
As illustrated in FIG. 2, a plurality of thrust reverser doors 7 may be incorporated into the cowling, such doors being circumferentially spaced around the periphery of the cowling. A longitudinal beam portion 18 extends axially between forward part 4 and the rear part 3 of the cowling between adjacent thrust reverser doors 7 to provide structural rigidity to the cowling and to provide pivot mounting points for attaching the doors 7 to the cowling. U.S. Pat. No. 3,605,411, and French Patents 1,482,538 and 2,030,034 illustrate typical, known thrust reversers.
It is known to utilize one linear actuator per thrust reverser door affixed to the cowling and the thrust reverser door to move the door between the forward and reverse thrust positions, as illustrated in the aforementioned French Patent 1,482,538.
Conventionally, the thrust reverser control system has a hydraulic power source and generally consists of a common control unit, one linear actuator per movable element, position signalling means, and several redundant locks to preclude unintentional movement of the thrust reverser doors toward the reverse thrust positions. The redundant locks typically comprise a plurality of mechanical locking systems to provide three lines of defense against inadvertent deployment of the thrust reverser doors. A primary latch latches the forward portion of the thrust reverser doors to the cowling so as to retain the doors in their forward thrust positions. Secondary locks may be integrated into the thrust reverser door actuators. The secondary latch retains the thrust reverser doors or movable elements in their forward thrust positions should the primary latch malfunction. Typically, the secondary lock may comprise claws within the linear actuator to grip various portions of the linear actuator to prevent the actuator from moving to its reverse thrust position. The claws may remain withdrawn, or in an idle position, during normal operation of the system, and only function when there is a malfunction of the primary lock. Since the secondary lock is located within the linear actuator body, it is impossible to inspect the secondary lock for any malfunctions. Thus, in the absence of such inspections, the secondary lock may malfunction when called into play.
A third lock may be actuated by a power source different from that of the primary and secondary locks. The third lock may be located in side portions of the thrust reverser doors and, similar to the secondary locks, may be passive during normal operation of the thrust reverser. The third locks typically do not physically touch the latch and the movable element when the thrust reverser is in the forward thrust configuration.
The known locking systems require parts having very small tolerances and which are, therefore, costly to manufacture. At the same time, the total number of movable parts degrades the overall reliability of the locking systems. Operating all of the system elements requires a specific hydraulic connection for each component, thereby increasing the number of connections and the amount of hydraulic piping necessary. Since hydraulic fluid is notoriously corrosive and flammable, the number of connections increases the probability that a leak will occur and requires increased maintenance to maintain the integrity of the hydraulic system.